Stabilizing of photographic silver halide emulsions with acyl phenyl hydrazides



United States Patent sellsch'aft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Feb. 24, 1965, Ser. No. 435,067

Claims priority, applization Germany, Mar. 5, 1964,

Claims. (61. 96-109) The invention relates to photographic emulsions and particularly to a process for stabilizing photographic silver halide emulsions by the addition of phenylhydrazides of aliphatic carboxylic acids.

Silver halide emulsions prepared by the usual processes undergo a marked reduction in their sensitivity, a flattening in the graduation and increased fogging when stored under tropical conditions. The sensitivity nuclei and the latent image nuclei of exposed silver halide emulsions are not stable in storage. Stabilization of the latent image is of particular importance in multilayered color photography since the various additives in the individual layers, such as color components, sensitizers etc. cause varying degrees of alteration of the latent image on storage and thus cause a shift in the color balance.

It is known to add hydrazinium salts or hydrazine compounds to photographic silver halide emulsions, as described for instance in British Patent No. 598,106 for increasing the speed or contrast or both of such emul- SlOIlS.

However, the hydrazine compounds customarily employed in photographic emulsions show practically no stabilizing effect. They have even been used for fogging silver halide emulsions to render reversal exposure of the material unnecessary. Moreover, many hydrazine compounds impair or even completely prevent hardening of the gelatin by ordinary hardening agents.

It is an object of the present invention to provide photographic silver halide emulsions, the latent image of which is stabilized. A further object is to provide a new method for stabilizing the latent image of photographic silver halide emulsions. Other objects will appear from the following description of our invention.

We now have found that the stabilization of the latent image specks and of the so-called sensitivity specks in particular of silver halide emulsions which are afterripened and the latent image specks of which are situated essentially on the surface of the silver halide grain can be achieved even under extreme conditions of storage such as storage under tropical conditions by adding phenylhydrazides of aliphatic, saturated or unsaturated monoor polycarboxylic acids having preferably up to 12 carbon atoms more particularly up to 5 carbon atoms per phenylhydrazol unit, to the photographic emulsions. The compounds are characterized in that they contain at least once the following group wherein the phenyl nucleus can be substituted as desired by any groups that are photographically inert. These include, for preference, alkyl radicals having up to 5 C- atoms, alkoxy radicals, preferably of the same type as 3,386,831 Patented June 4, 1968 See the alkyl radicals, halogen atoms such as chlorine or bromine and carboxyl groups.

The group given in the-above formula is linked to straight chained or branched, saturated or unsaturated aliphatic radicals.

The following compounds have been found suitable for use according to our invention:

acetic acid phenylhydrazide, acetic aoid-p-tolylhydrazide, propionic acid phenylhydrazide, butyric acid phenylhydrazide, methacrylic acid phenylhydrazide, isobutyric acid phenylhydrazide, maleic acid-bis-phenylhydrazide, fum'aric acid-bis-phenylhydrazide, itaconic acid-bis-phenylhydrazide, glutaric acid-bis-phenylhydrazide, citric acid-tri-phenylhydrazide, polyrnethacrylic acid phenylhydrazide, adipic :acid-bis-phenylhydrazide.

The silver halide emulsions are produced in accordance with common practice. The preparation involves 3 separate steps: (1) precipitation of the silver halide and physical ripening in the presence of gelatin, (2) freeing of the emulsion of excess water-soluble salt usually by washing and (3) after-ripening or chemical ripening to obtain the desired speed or sensitivity.

The substances can be added at any desired stage to the light-sensitive silver halide emulsion layer or if desired to auxiliary layers.

In the preparation of the photographic emulsions of the present invention the phenylhydrazides are advantageously incorporated in the finished emulsion after the chemical ripening. It is'convenient to add the stabilizers of the present invention from solutions in appropriate solvents. The solvent should, of course, be completely free from any deleterious effect on the silver halide emulsion. Water or lower aliphatic alcohols or admixtures thereof have proven satisfactory as solvents for the majority of the stabilizers of the invention. The concentration of the stabilizers in the emulsion can vary widely from about 0.1 to 20 g. per mol of silver halide, their specific concentration will vary according to the type of the light-sensitive emulsion and according to the effects desired. Preferred are concentrations of between 1 and 10 g. per mol of silver halide. The most suitable concentration for any given emulsion will be apparent upon making the test customarily used in the art.

It has surprisingly been found that while all the usual photographic properties are retained (these are determined largely by the structure of the silver halide emulsion), there is obtained in addition an excellent stabilization of the latent image specks. Even when the photographic materials produced by the process according to the invention are stored over a considerable period at normal temperature or under the conditions of high temperature and humidity which may occur in tropical climates for example, no fading of the latent image specks takes place.

The emulsions for which the phenylhydrazides according to the invention are used, are after-ripened in accordance with common practice. The emulsions essen-' tially form a latent image on the surface of the silver halide grain.

The emulsions may contain the customarily employed silver halides such as silver chloride, silver bromide or mixtures thereof, which may contain a small amount of about up to mol percent of silver iodide. Suitable as binding agents for the light-sensitive layer are the usual hydrophilic binders such as carboxymethylcellulose, polyvinyl alcohol, vinyl pyrrolidone, alginic acid and its salts, esters or amides and especially gelatin.

The emulsions stabilized in accordance with the present invention can be chemically sensitized by any of the accepted procedures. The emulsions can be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Suitable compounds are well known in the art. The emulsions can also be sensitized with gold salts as described by R. Koslowsky Z. wiss. phot. 46, 65-72 (1951). The emulsions can also be chemically sensitized with reducing agents such as stannous salts, polyamines, sulfur compounds, such as described in the US. Patent 1,574,944, polyethylene oxides and the like. The emulsions can also be optically sensitized with the ordinary sensitizing dyes, cyanines or merocyanines. The emulsions can be stabilized with any of the known stabilizers such as mercury compounds, triazoles, azaindenes, such as disclosed by Birr in Z. wiss. phot., vol. 47 (1952), pages 2-28. The emulsions may be hardened by any suitable hardener, such as formaldehyde and halogen-substituted aliphatic acids such as mucobromic acid.

Example 1 A highly sensitive silver iodobromide gelatin emulsion having an iodine content of 4 mols percent and a silver nitrate/gelatin ratio of 1:1 is produced by the usual method, washed and after-ripened to maximum sensitivity with the use of sulfurand gold sensitizers.

The pH of the finished emulsion is 6.4. Before pouring onto the usual photographic surfaces, the customary stabilizers such as 200 mg. of 1,3,3a,7-tetraaza-4-hydroxy-6- methylindene per liter emulsion, wetting agents such as 30 ml. of a 7.5% aqueous solution of saponin per liter emulsion and hardening agents such as ml. of a 10% aqueous formaldehydre solution per liter emulsion are added to the emulsion.

The above emulsion was divided into several portions and phenyl hydrazides of the present invention were added from aqueous or methanolic solution in the amounts Sample:

G. N-methyl-p-aminophenolsulfonate 3.5 Sodium sulfite sicc. Hydroquinone 9 Soda sicc; 40 Potassium bromide made up to 1000 ml 3.5

The results of the sensitometer tests are shown in the following Table 2:

TABLE 2 Fresh Stored Sensi- Fog Grada- Sensi- Fog Gradativity tion tivity tion PartA 0.10 1.7 50 0.13 1.45 PartB 100 0.09 1.7 75 0.09 1.6 Part0 100 0.09 1.7 83 0.09 1.7 PartD 100 0.09 1. 7 75 0. 09 1.0 PartE 100 0.09 1.8 83 0.09 1.8 PartF 100 0.09 1.8 as 0.09 1.8

Before casting, a silver halide gelatin emulsion was treated with 0.3 g. of chloromucic acid per kg. of emulsion and 3.4 g. per silver halide mol of the hydrazine compound given below. After casting, drying and 48 hours storage, the melting point of the layer was determined. The results are given in Table 3.

TABLE 3 Substance added Melting point of the emulsion 1- Without additive Above 100 C.

Above 100 C.

Whereas the phenyl substituted carboxylic acid hydrazides according to the invention given under (2) do not impair the hardening effect, hydrazides which have a free NH group, alkyl-, cycloaykyland aralkyl-substituted hydrazides and acyl hydrazones prevent hardening of the gelatin. Compounds of the type given under (3) are therefore of limited utility as additives for photographic layers.

Example 3 Numerous hydrazine compounds which also do not prevent hardening of gelatin were added to a silver halide emulsion as described in Example 1 and their effect compared with phenylhydrazides according to the invention. Chloromucic acid was used as hardening agent. In all the samples, the melting point of the layer was above 100 C.

The results of the tests are shown in the following Table 4:

TABLE 4 Quantity Fresh Stored Substance added in g. per

1 mol Ag Sensi- Fog Grada- Sensi- Fog Grade.-

tivlty tion tivity tion Without additive 100 0.10 1. 7 50 0. 13 1. 4'

0113- O-NH--NH 1. 7 100 0. 09 1. 7 75 0. 09 1. a 3.4 100 0. 09 1.7 33 0.00 1. 7

om-oH-o O-NH-NHQ 1. 7 100 0. 09 1 s 75 0. 09 1. s 3.4 100 0.09 1 8 83 0.09 1.8 CH3 Q0 0NHNH- 1. 7 100 0. 11 1. 0 50 0. 13 1. 45

i 3.4 100 0.11 1.4 50 0.15 1. 3 0.11 0-0 O-NH-NH 1. 7 100 0. 09 1. s 50 0.12 1. 8 3.4 100 0. 09 1. s 66 0.12 1. 3

HzN-C ONHNH 1. 7 100 0. 10 1. 4 50 0. 13 1.

0 111-0 O-NHNH--C O-C1H7 1. 7 100 0. 10 1. 9 0. 1a 1. 8 a. 4 100 0. 10 1. 7 50 0. 11 1.8

CH; CH -CONH-1\/ 1.7 100 0. 09 1 s 50 0.13 1 7 3.4 100 0.10 1 s 50 0.13 1 7 CH3 CH -C 0NHN 1. 7 100 0. 0s 1. 8 50 0. 12 1. 7 Q 3. 4 100 0. 0s 1. s 0. 12 1. 7

' 1. 7 200 0. s0 0. 8 Black l: N-CHz-C 0-NH-NH Cl 3. 4 Black CH: 69 6 1. 7 100 0. 10 1. 5 Black l 3. 4 100 0. 11 1. 5 Black HzN-N-CHrCHa 0104 CH3 0 H1 1. 7 100 0. 13 1. 6 Black I 6969 e 3. 4 117 0.13 1. 7 Black H1N--N-(CH2)a-N-NHz 20104 1 Strong fogging.

The above table shows that only the phenylhydrazides of the present invention stabilize the latent image specks or the sensitivity of the silver halide emulsion. Other phenylhydrazides either have no stabilizing effect or cause a strong fogging of the silver halide emulsion layers.

Example 4 A multilayer colorphotographic element is produced which includes a blue-sensitive silver halide emulsion layer containing 3-(p-stearyl-aminobenzoyl-acetamino) isophthalic acid as yellow coupler, a green-sensitive silver halide emulsion layer containing l-(3'-sulfo-4'- phenoxy)- phenyl-3-heptadecyl-pyrazolone-(5) as magenta coupler and a red-sensitive silver halide emulsion layer containing l-hydroxy 2 naphthoic acid-(2'-(methyl-n-octadecylamino)-5'-sulfonic acid)-anilide as cyan couple-r. The silver halide of the three light-sensitive layers essentially con sists of silver bromide. In addition to these couplers, the usual casting additives as described by Glafkides: Photographic Chemistry, vol. 2 (Fountain Press, London), pages 564-568 for reverse color films are added to the three layers (Sample I).

A second multilayer colorphotographic element is produced in the same way but 100 ml. of a 1% aqueous solution of acetic acid phenyl hydrazide is added per kg. of the emulsion containing the yellow coupler before the upper layer is cast (Sample II).

Both films are exposed behind a grey step wedge and stored for 8 weeks at about 20 C. and relative humidity of about TABLE 5 Fresh Stored Sample Sensitivity Color Sensitivity Color I 100 Neutral 50 Yellowish II 100 do Neutral.

The blue-sensitive emulsion layer was particularly subject to fading with respect to the latent image specks. This is clearly apparent from the yellowish color of the stored Sample I, which have a yellowish tint because of the reversal development. With stabilized Sample II a neutral grey image is obtained.

The phenylhydrazides utilized in accordance with the present invention are prepared by the conventional methods for the production of hydrazides of carboxylic acid. Suitable methods are disclosed in the handbook Methoden der organischen Chemie by Hou'ben-Weyl, 4th edition, volume 8, Part III, pages 676-680, published by Georg Thieme Verlag, Stuttgart 1952.

We claim:

1. An after-ripened photographic silver halide emulsion the silver halide grains of which are essentially surface-sensitive and which contains a stabilizing amount of a fl-mono-phenylhydrazde of an aliphatic carboxylic acid.

2. A photographic silver halide emulsion as defined in claim 1 in which the carboxylic acid is a m-ono-carboxylic acid.

3. A photographic silver halide emulsion as defined in claim 1, wherein the phenylhydrazide is characterized by the following formula:

R is an aliphatic radical having up to 6 carbon atoms of the groups consisting of saturated alkyl and olefinically unsaturated alkyl, y stands for a whole number from 1 to 3 and X represents a substituent of the group consisting of hydrogen, alkyl, alkoxy, halogen and carboxyl.

4. A photographic silver halide emulsion as defined in claim 3, in which the phenylhydrazide is the 8-monophenylhydrazide of acetic acid.

5. In a process of making photographic images including the steps of exposing to the object to be reproduced a photographic element comprising a supported lightsensitive silver halide emulsion layer, developing and fixing the exposed element, the improvement consisting of performing the process with a photographic element containing a stabilizing amount of a p-mono-phenylhydrazide of an aliphatic carboxylic acid.

6. A process as defined in claim 5, wherein the carboxylic acid is a monocarboxylic acid.

7. A process as defined in claim 6, wherein the phenylhydrazide has the formula 8 wherein:

R is an aliphatic radical having up to 6 carbon atoms of the group consisting of saturated alkyl and olefinically unsaturated alkyl and X represents a substituent of the group consisting of hydrogen, alkyl, alkoxy, halogen and carboxyl.

8. A process as defined in claim 7, wherein R is methyl.

9. A photographic silver halide emulsion containing from about 0.1 to about 20 grams per mole silver halide of a substituted or unsubstituted B-mono-phenylhydrazide of an aliphatic carboxylic acid, said B-mono-phenylhydrazide when substituted having a phenyl substituent selected from the group consisting of alkyl having up to 5 carbon atoms, alkoxy having up to 5 carbon atoms, halogen and carboxyl and said aliphatic carboxylic acid being a monocarboxylic or polycarboxylic, saturated or unsaturated acid.

10. A method of stabilizing the latent image specks in a photographic silver halide emulsion comprising adding to said photographic silver halide emulsion from about 0.1 to about 20 grams per mole silver halide of a substituted or unsubstituted B-mono-phenylhydrazide of an aliphatic carboxylic acid, said fl-mono-phenylhydrazide when substituted having a phenyl substituent selected from the group consisting of alkyl having up to 5 carbon atoms, alkoxv having up to 5 carbon atoms, halogen and carboxyl and said aliphatic carboxylic acid being a monocarboxylic or polycarboxylic, saturated or unsaturated acid.

No references cited.

NORMAN G. TORCHIN, Primary Examiner.

J. R. EVERETT, Assistant Examiner. 

1. AN AFTER-RIPENED PHOTOGRAPHIC SILVER HALIDE EMULSION THE SILVER HALIDE GRAINS OF WHICH ARE ESSENTIALLY SURFACE-SENSITIVE AND WHICH CONTAINS A STABILIZING AMOUNT OF A B-MONO-PHENYLLHYDRAZDE OF AN ALIPHATIC CARBOXYLIC ACID. 